<div id="app">
   <navbar ></navbar>
   <pagefooter ></pagefooter>
  </div>

  Vue.component('navbar',{
    template:'<div>{{navs}}</div>',
    data:function () {
     return {
      navs:1
     }
    }
   });
  Vue.component('pagefooter',{
    template:'<div>{{footer}}</div>',
    data:function () {
     return {
      footer:11
     }
    }
   });

  <div id="app">
   <navbar ref="navbar"></navbar>
   <pagefooter ref="pagefooter"></pagefooter>
  </div>
   new Vue({
    el:'#app',
    created:function(){
     
    },
    mounted:function () {
     this.$refs.navbar.navs=222
     //ready,
     //这里怎么直接访问navbar的navs和pagefooter的footer值呢，
      console.log(this.$refs.navbar.navs);
      console.log(this.$refs.pagefooter.footer);
    }
   })

<div ref="demo"></div>

document.querySelector('[ref=demo]');